1. Field of the Invention
The present invention relates to a sample injecting device for importing a liquid sample into an analysis apparatus, in particular, to a sample injecting device including a needle, connected to a flow path switching valve, and a port.
2. Description of Related Art
In order to analyze multiple samples, a sample-injecting device for automatically introducing the sample into an analysis apparatus such as a liquid chromatograph in a defined sequence has already been used. FIG. 5 (a) is a schematic view of a liquid chromatograph. The liquid chromatograph includes a liquid delivery device 10, a sample injecting device 20, a separating and detecting unit 30, and a controlling and parsing unit 40, wherein the sample injecting device 20 is disposed between the liquid delivery device 10 and the separating and detecting unit 30. The separating and detecting unit 30 includes an analytical column 31 or a detector 32, and forms various flow paths corresponding to different analytical aims; and the separating and detecting unit 30 functions as an analyzing unit. The liquid delivery device 10, the sample injecting device 20, and the separating and detecting unit 30 are controlled by the controlling and parsing unit 40. Furthermore, the controlling and parsing unit 40 receives signals from the detector 32, parses the sample in a qualitative and quantitative manner, saves the parsed data or generates an analysis report and outputs the analysis report.
The sample injecting device has two injection modes: “total-volume injection”, in which all measured sample is injected from a sample vial, and “loop injection”, in which a part of the measured sample is injected into a sample loop from a sample vial (Patent Document 1 and Patent Document 2 etc.). In the field where only an extremely low amount of sample can be extracted, in order to analyze the extracted sample without any waste, the sample injecting device of total-volume injection has been widely used.
FIG. 5 (b) is a schematic view of internal flow paths in a sample injecting device 20 of total-volume injection. The sample injecting device 20 forms flow paths with a six-port two-position valve 21 and a six-position valve 22 as the center. The flow path of the mobile phase solution from the liquid delivery device 10 to the sample injecting device 20 is firstly connected to one port of the six-port two-position valve 21. Starting from the sample loop 23, passing through a needle 24 disposed at the front end of the sample loop 23, and then through an injection port 25 with the needle 24 inserted therein, the flow path from the upstream side of a liquid delivery device 10 is communicated with a flow path towards the separating and detecting unit 30 of the downstream side. Thus, all sample filled in the needle 24 to the sample loop 23 is introduced into the separating and detecting unit 30. A flow path communicated with a cleaning liquid container, a flow path communicated with a measuring pump 26, and a flow path communicated with a cleaning port 27 are connected on the six-position valve 22, wherein the measuring pump 26 sucks in the cleaning liquid from the cleaning liquid container or sucks in the sample from the sample vial 28; the cleaning port 27 is provided for the insertion of the needle 24 so as to clean the needle; furthermore, the needle 24 is communicated with the flow paths of the sample loop 23 and the measuring pump 26 through the six-port two-position valve 21 (Patent Document 3 and Patent Document 4, etc.).
When the sample is injected into an injection unit, the front end of the needle is lowered so that the front end of the needle is inserted into a correct position of the injection port (flow path hole). However, in circumstances when the front end of the needle is not lowered to the correct position of the port, the front end of the needle is worn, or the injection port is contaminated by the front end of the needle. Thus, the position of the needle must be adjusted so that the needle is lowered to the correct position of the injection port. However, recently in order to increase throughput of analysis, the action speed of the needle becomes higher. Therefore, it is necessary to make correct adjustments to the position of the needle. Patent Document 5 provides the following technology: position alignment is carried out at a speed slower than that of a common action, and then, the upward and downward actions are repeated for many times at a common speed (aging actions), so that the position relation of the needle and the injection port is memorized in the device.
Therefore, after the needle is squeezed into the injection port, the sample injecting device maintains a watertight state. However, in order to maintain the needle and the injection port in a watertight manner, materials with a low mechanical strength are generally used to faun one of the needle and the injection port, so as to maintain the sealed state through such design. In most circumstances, the needle has to perforate the hood of the sample vial, and thus, the needle uses a hard material (for example, stainless steel as a base material), and the port uses a relatively soft material (for example, polyetheretherketone (PEEK) and resin).